Variable compression ratio internal-combustion engine



May 22, 1951 H. J. KRATZER VARIABLE COMPRESSION RATIOINTERNAL-COMBUSTION ENGINE 2 Sheet s-Sheet 1 Filed April 25, 1947 IN VEN TOR.

V R r K m I a T r T m A 5 m H? Y B H. J. KRATZER May 22, 1951 VARIABLECOMPRESSION RATIO INTERNAL-COMBUSTION ENGINE 2 Sheets-Sheet 2 FiledApril 25, 1947 m. R mm H m m mJ 0 ELM Patented May 22, 1951 VARIABLECOMPRESSION RATIO IN TERNAL-CQMBUSTION ENGINE Herbert J. Kratzer, St.Louis, Mo.

Application April 25, 1947, Serial No. 743,751

4 C a ms.

The invention relates to internal combustion engines and moreparticularly to variable compression ratio engines of the kind describedin Patent No. 2,399,276, issued April 30, 1946 to the present applicant.

The engine described in the above patent has a movable head to vary thecylinder volume for the more efficient combustion of fuel ofapproximately a given octane rating, and the compression ratio is variedautomatically throughout a single range of head movement to compensatefor different throttling effects. Different throttling may be due tomanual throttling, decreased air density at higher altitudes, orthrottling incidental to high engine speed. Any of these throttlingeffects starve the cylinders, i. e., results in the fuel charge beinginsufficient for an eflicient compression pressure. I The main object ofthe present invention is to. vary the operative ranges of compressionratios of a variable compression ratio engine to economically employfuels of different octane ratings under the operating conditionsmentioned above and, in addition, to compensate for temperature changes.

Another object is to readily vary the operative range of compressionratios by a conveniently located manual control.

Another object is to employ combustion chamber pressures to directly andautomatically vary the combustion chamber volume of respective cylinderswithin a given range so that the combustion chamber volume approximatelycorresponds to the instant volumetric efliciency of the refuelingoperation.

, Another object is to provide the engine with simple means to adjustthe combustion cham ber volume of each individual cylinder, independently of the other cylinders, to compensate for manufacturingvariations, carbon deposits, wear or other factors producing unequalcombustion chamber performance.

Another object is to automatically select a predetermined minimumcompression ratio for the duration of the engine starting operation.

Another object is to maintain all engine spark plug electrodes at thedesired temperature during all operations, except at starting, of theengine by immersing the plug porcelains in an insulating coolant fluid,such as oil from the engine crank case, and to maintain this coolantfluid at a temperature sufficient to boil on condensation products andthus recondition the fluid and preserve its dielectric properties.

Another object is toposition the spark plugs 2 between the intake andexhaust valves and substantially centrally of the combustionchambers,irrespective of the prevailing compression ratio, to provide forreliable ignition and minimum flame travel.

Another object is to provide for the reliable ignition of economicalfuel mixtures due to a minimum degree of new charge dilution with hotresidual combustion chamber gases espe[-. cially at idle and lighttorque loads.

Another object is to cause turbulence within the combustion chambers toinsure thorough mixing of the combustion chamber gases before ignitionand to increase flame speed after ignition.

Another object is to cause turbulence during flow of combustion chambergases to cylinder bores after ignition to facilitate combustion of thegases early in the expansion stroke.

These and other objects will be apparent to those skilled in the artfrom the following'description and accompanying drawings, in which:

Figure l is a plan view of an internal combustion engine constructedaccording to the invention.

Figures 2 and 3 are detail vertical transverse sections drawn toenlarged scale and taken approximately on the lines 22 and respectively,of Figure 1.

Figure 4 is a detail horizontal section taken approximately on the line4- of Figure 3.

An internal combustion engine constructed according to the inventioncomprises a plurality of working cylinders I such as may be formed, forexample, in a single block Ia. Each cylinder has a reciprocating piston2 connected by a rod 3 to the engine crankshaft (not shown). Aconventional intake valve ll and adjacent exhaust valve 5 are associatedwith each cylinder I.

A cylinder head 8 is mounted on block la and forms a water jacket withouter side walls 9. A vertical cylindrical bore IE3 through the head isabove and partially overlaps each working cylinder I but is offsettowards its associated valves 4 and 5. Slidable in each here is aninverted head piston I l. The bottom face of head 8 is recessed overvalves 4 andfi to form pockets 4a and 5a (Figure 4). The bottom face ofhead piston II is recessed to form a pocket Ila. Pockets la, 5a and ilcrform the major portion of the cylinder combustion chamber 1, the wallsof which converge towards the rem e side of he ork y nd r to form,

a restricted passageway Ia into the cylinder and, as so shaped, increaseturbulence thereby promoting more complete combustion as early in theexpansion stroke as possible.

Each head piston II is connected by a link I2 and pin I3 to a rocker armI5 keyed to shaft I6 journalled in bearings I! on head 8. One rocker armI5 has an extension it provided at its free end with an adjustable pinI9 engaging a saddle on the upper end of a helical coil spring 2| seatedin the bottom of a hollow inverted piston 22 slidably in a springcylinder 23 at the side of cylinder head 3. Preferably spring cylinder23 is mounted on a bracket 24 including side walls and forming a pocket33 for the purpose explained below.

During normal engine operation, the positions of head pistons II aredetermined'by the sum of l the pressures in all working cylinders I andby the thrust of compression spring 2| which resists and balances theworking cylinder pressures. With small crankshaft torques, the sum ofthe pressures in working cylinders I is relatively small permittingspring 2| to move head pistons downwardly in cylindrical bores Ill anddecrease the combustion chamber volume to provide higher compressionratios, At large crankshaft torques, the sum of the pressures in workingcylinders is relatively large so that head pistons I move upwardly whilecompressing spring 2| and provide lower compression ratios due to theenlarged combustion chambers. This automatic determination ofcompression ratios provides for the optimum compression ratio at anyprevailing speedtorque output of engine and compensates for barometricvariations.

Oil from the crankcase is pumped through conduits 25, 25a in a block'21, into spring cylinder 23 below spring piston 22 and piston 22 israised from the solid line position shown inFigure 2 to other positionsas indicated by the broken lines in Figure 2. The lower end of spring 2|is raised and its tension is increased, whereby head pistons II movedownwardly in cylindrical bores l0 against the prevailing workingcylinder pressures and decrease the volume of the combustion chambers toincrease the compression ratios. The position of spring piston 22 inspring cylinder 23 is determined by a valve sleeve 26 slidably mountedin block 21 and extending upwardly into spring cylinder 23 and into adome-shaped portion 28 of spring piston 22. The upper end of valvesleeve 26 is slotted at 30. Valve sleeve 26 may be raised or loweredrelative to spring piston. 22 by an arm 29 pivoted in block 21 and linkconnected to valve sleeve 26. Spring piston 22 automatically moves to aposition in spring cylinder 23 at the.

upper end of valve sleeve 26 and uncovers the lower portions of slots3|] so that excess oil pumped into spring cylinder 23 escapes throughslots 30 and flows through the interior of valve sleeve 26 into a cavity21a in block 21 and through a conduit 3| to the crankcase.

Spring cylinder 23 has ports 32 in its upper.

sides so that oil leaking past spring piston 22 is returned to thecrankcase through pocket 33, drain 34, cavity 21a and conduit 3|.

The most economical compression ratio for a particular fuel,irrespective of its octane rating, is the highest compression ratiowhich provides for smooth engine operation without knocking as evidencedby audible pinging. The engine may be economically adapted to fuel ofany octane rating by operating lever 29 manually,

preferably from the dash of the car, to provide 4. maximum tension ofspring 2| without causing the engine to knock.

For fuels of low octane rating, spring piston 22 is lowered in springcylinder 23 and the tension of spring 2| is decreased to operate theengine in a range of decreased compression ratios. For fuels of highoctane rating, spring piston 22 is raised in spring cylinder 23 and thespring tension is increased to operate the engine in a range ofincreased compression ratios.

A rib 43 on head 8 engages an adjustable screw 44 at the end of anextension 42 rigid with one of the rocker arms I5 and limits downwardmovement of head pistons and provides a maximum desired compressionratio for combustion chambers I. An adjustable stop Mi supported by abracket 4| attached to head 8 engages the end of extension 42 and limitsupward movement of head pistons I and provides a minimum desiredcompression ratio for combustion chambers I. In the event spring 2|breaks, the engine'would continue to function as a conventional engineat the minimum compression ratio. The maximum and minimum compressionratio stops preferably are adjusted to provide for a plurality of rangesof normal operating compression ratios for fuels of various octaneratings.

When the ignition circuit is opened and the engine is stopped, a plugvalve 35 is moved to open position by an arm 35a, as shown by the solidlines in Figure 2, to quickly drain oil from spring cylinder 23 belowspring piston 22 through conduit 25a, cavity 21a and conduit 3| to thecrankcase, whereupon spring piston 22 moves rapidly to the solid lineposition shown in Figure 2, head pistons move downwardly until screw 44engages stop 43, and spring 2| extends sub stantially to its freelength.

During starting of the engine, when the crank shaft is being turnedslowly by the starter, and

before anycyclic firing, only compression pressures contract spring 2|which offers but little II which move approximately midway betweenmaximum and minimum combustion chamber volumes as determined by stops4|! and 43. Initial ignition in combustion chambers I increases the sumof the combustion chamber pressures sufficiently to move headpistonsupwardly to their maximum combustion chamber volume. After the motoroperates through a few revolutions, intake manifold pressures andresulting combustion chamber pressuresdecrease, whereupon head pistonsare moved downwardly by spring 2| approximately midway between maximumand minimum combustion chamber volumes. spring piston 22 is raised inspring cylinder 23 by oil under pressure from the engine lubricatingsystem until slots 30 in valve sleeve 26 are uncovered. Displacement ofspring 2| moves head pistons downwardly decreasing the combustionchamber volume until the spring tension is balanced by the sum of thecylinderpressures- With further operation of the engine,

other workingv cylinders. The volume of a compression chamber 1 may bedecreased by loosening the nut on eye bolt [4 and tightening the nut oneye bolt Ma to shift element i511 aboutshaft l6 relative to.- keyedelement 150; whereby head piston II is moved downwardly a short distancein head bore it. The nuts on eye bolts 14 and Ma then may be locked toretain head piston H in adjusted position.

Another of the arms l has an integral extension 50 provided with abifurcated free end connected to one end of a link 5| by a pin 5Ia. Theopposite end of link 5| is connected by a pin 5!?) to a dash pot piston53 slidably mounted in an oil-filled dash pot cylinder 55. Cylinder 55is attached to head 8 by webs 52. Dash pot piston 53 has a spiral Acmethread-shaped depression 54 about its circumference forming an elongatedpassageway bypassing the piston, thus enabling gradual movement of thedash pot piston in the dash pot cylinder. A plurality of equally spacedconduits 55 connect respective ends of cylinder 55 through upper andlower ports 51 and 58. Upper ports 5? normally are closed by the skirtportion of a cap 59 mounted rotatably on cylinder 55 and havingapertures 5!! through the skirt portion. movable into registry withupper ports 51 to allow oil to flow freely through conduits 5B whenevermore rapid adjustment of piston 53 is desired. The dash pot dampsintercyclic firing impulses transferred to shaft 16 during normal engineoperation so that the algebraic sum of the rapidly changing cylinderpressures will be counterbalanced by spring 2| whereby head pistons IIand shaft It will move only when a change in engine torque occurs.

A spring 5! urges cap 59 against stop 62 in which position the capcloses ports 51. The cap may be moved to open said ports temporarilywhen the starter is actuated or when the throttle is opened quickly.This opening of ports 51 is effected through link 63 which has a rod 64leading direct to the starter (not shown). Link 63 is connected to thethrottle by a dash pot unit including a chamber 55, a piston 65a thrusttowards the upper end of the chamber by spring 651) and a rod 650connected to a lever 66 pivoted on the engine. A rod 66a leads to thethrottle (not shown). The pin and slot connections between link 63 andthe starter rod and the throttle rod enable the link to be moved byeither rod independently of the other. When link 63 is moved from thesolid line position shown in Figure 4 to the dotted line position byslow movement of the throttle, oil passes piston 65a and the position oflink 63 is not changed. When the throttle is opened rapidly, oil inchamber 65 cannot pass piston 65a rapidly enough and chamber 65 ismoved, thus shifting cap 59 to open ports 51 and allow oil in dash potcylinder 66 to bypass piston 53 through ports 5'! and 58 so that headpistons H respond more rapidly to pressure changes in cylinder I.

The space H between working piston 2 at the top of its stroke and theoverlying flat portion of cylinder head 8 preferably is a minimum.During the last part of the compression stroke of a working piston 2,the compressed gases above the piston are finally displaced from betweenthe top of working piston 2 and the overlying portion of cylinder head 8through passageway 1a into combustion chamber 1 with considerablevelocity approximately in the directions indicated by the arrows inFigure 3, causing desirable turbulence of the gases in the combustionchamber to facilitate rapid flame travel from the spark gap through thecombustion chamber as the working piston completes its upwardcompression stroke and starts downwardly on the expansion stroke. As thepiston continues to accelerate in itsdownward movement, the ignitedcharge moves from the combustion chamber through the relatively narrowpassageway la into working cylinder l' at an increased velocity. Thisdownwardly directed flow of ignited gas causes further turbulence in theworking cylinder and facilitates the continued rapid combustion causingmaximum expansion pressure at the time the piston and crankshaft arepositioned for maximum conversion of cylinder pressure into turningtorque.

A spark plug i3 is threaded into the pocket portion of head piston Hbetween the intake and exhaust valves so that the intake charge coolsthe spark gap electrodes. Plug '83 is positioned substantially centrallyof the combustion chamber. The spark gap eiectrodes of spark plug 13 aremaintained substantially at a desired temperature by immersing the plughead in coolant oil contained in head pistons II. The oil prevents hotspots on the portion of head pistons l I forming parts of the combustionchamber walls by convecting heat from these parts to the side walls ofhead pistons I l for transmission to water jacketed head bores in. Theoil is maintained at a temperature sufficiently high to boil oifcondensation products and thus reoondition the oil and maintain itsdielectric properties to prevent short-circuiting over the plugporcelains. Oil from the crankcase may be circulated continuouslythrough head pistons II as part of the oil filter system forcontinuously reconditioning the oil. High tension ignition cables [5connect the immersed spark plugs 13 to the distributor (not shown).

The skirts of pistons ll always extend above the sides of head bores Itto prevent oil seeping into combustion chambers 1 when the engine isstopped. A cover (not shown) may be provided for excluding dust andother injurious matter from the mechanism described. A raised rib 45along the top periphery of head 8 directs spilt oil to drain into pocket33 to be returned to the crankcase.

The details of the construction may be varied substantially withoutdeparting from the spirit of the invention, and the exclusive use ofthose modifications coming within the scope of the claims iscontemplated.

What is claimed is:

1. In an internal combustion engine, a cylinder, a movable wallassociated with said cylinder to change its compression ratio inaccordance with cylinder pressures, a spring resisting the cylinderpressures and automatically positioning said wall during normal engineoperation to determine the compression ratios within a predeterminedrange, a seat for said spring, hydraulic means to move said seat duringengine starting operation to change the pressure of said spring, andmanually adjustable means for controlling said hydraulic means to varythe seat position to change the spring pressure and thereby change theoperative range of compression ratios.

2. In an internal combustion engine, a cylinder, a movable wallassociated with said cylinder to change its compression ratio inaccordance with cylinder pressures, a spring resisting the cylinderpressures and automatically positioning said wall during normal engineoperation to determine the compression ratios within a predeterminedrange,

a piston seating said spring, a spring cylinder slidably receiving saidpiston, a hydraulic device actuated by fluid pressure, supplied by thenormal operation of the engine, to move said spring seating piston insaid spring cylinder to change the thrust of said spring, said deviceincluding a manually actuated positively adjustable ported sleevecontrol for varying the position of the spring seating piston andthereby varying the operative range of compression ratios.

3. In an internal combustion engine, a plurality of cylinders, a movablewall associated with each cylinder and movable inwardly and outwardly ofsaid cylinder to change its compression ratios, means to resist the sumof the prevailing cylinder pressures and to automatically position saidwalls in unison during normal engine operation to determine thecompression ratios, a pulsation eliminator to damp movement of saidwalls inwardly and outwardly of said cylinders, and means to render saidpulsation eliminator substantially inoperative during rapid engineacceleration and during engine starting.

4. In an internal combustion engine, a cylinder, a movable wallassociated with said cylinder to change its compression ratio inaccordance with cylinder pressures, a spring resisting the cylinderpressures and automatically positioning said wall during normal engineoperation to determine the compression ratios within a predeterminedrange, a seat for said spring, mechanism actuated automatically by theengine during its starting to move said seat to change the pressure ofsaid spring, and manually adjustable means to vary the seat position tochange the spring pressure and to change the operative range ofcompression rati s, 1

HERBERT J. KRATZER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 879,954 Fox Feb. 25, 1908 950,683Stranahan Mar. 1, 1910 1,106,210 Halterman Aug. 4, 1914 1,437,929Brockway Dec. 5, 1922 1,639,477 Wilson Aug. 16, 1927 1,757,907 Jamesonet a1 May 6, 1930 1,795,309 Marshall Mar. 10, 1931 1,812,572 Talbot June30, 1931 1,891,587 Wright Dec. 20, 1932 1,914,707 Wolf June 20, 19332,040,652 Gaty May 12, 1936 2,106,099 Jenkins Jan. 18, 1938 2,120,012Andreau June 7, 1938 2,145,017 Tsundeda Jan. 24, 1939 2,157,486Geisslinger et al May 9, 1939 2,399,276 Kratzer Apr. 30, 1946 2,420,117Weatherup May 6, 1947 2,500,409 Hawkins Mar. 14, 1950 FOREIGN PATENTSNumber Country Date 13,895 Austria Oct. 26, 1903 4,281 France Oct. 19,1905 2,015 Great Britain Jan. 27, 1909 25,736 Great Britain Nov. 9, 1912208,614 Great Britain Dec. 27, 1923

